For example, Patent Document 1 discloses a weather strip. The weather strip is attached to the periphery surrounding the opening of the back door of a vehicle body as a main body member. The weather strip serves as a sealing member that seals the boundary between the vehicle body and the back door as an opening-closing member. The weather strip is made of rubber and elastic. The weather strip has a welt portion, which holds the peripheral edge of the vehicle body opening, and a hollow sealing portion, which is connected to the welt portion. When the opening is closed by the back door, the back door contacts the weather strip, and the weather strip is elastically deformed and crushed due to the pressing of the back door. At this time, the weather strip is in intimate contact with the outer peripheral portion of the back door at the contact surface of the weather strip, and the vehicle body and the back door have satisfactory sealing property over the entire peripheral edge of the vehicle body.